Heater with a twist stopping device

Abstract: A draw-texturing apparatus comprises a heating device (3) for heating a running yarn (Y) and a false twisting device (5) disposed downstream of the heating device (3) for imparting twists to the yarn (Y). The apparatus further comprises a twist stopping device (11), disposed in the heating device (3), for stopping the run back of the twists imparted by the false twisting device (5). In the apparatus, drawing point of the yarn (Y) is not adversely affected by false twisting torque or vibration of the yarn (Y), and a textured yarn being free from unevenness in dyeability and having a high quality can be obtained by the apparatus.

Description: The present invention relates to a draw-texturing apparatus of a synthetic yarn made of such as polyester or polyamide. The present invention especially relates to a draw-texturing apparatus of a partially oriented yarn (POY) or an undrawn yarn (UD yarn) of such a synthetic yarn at a high speed more than 400m/min. In a conventional draw-texturing apparatus, a false twisting device is disposed downstream of a heating device, a twist stopping device for stopping run back of the twists imparted by the false twisting device towards the upstream of the heating device is disposed near an entrance of the heating device, and a bearing of the twist stopping device is a ball-and-roller bearing. The running yarn is wrapped around the twist stopping device so as to rotate the twist stopping device. In another conventional draw-texturing apparatus, as disclosed in Japanese Utility Model Application Laid-open No. Sho 59-73378, a single heating device is disposed at a draw-texturing region, and a twist stopping guide is disposed upstream of the heating device, i.e., at the entrance of the heating device. Thus, a yarn is drawn and false twisted while it is partially in contact with the yarn regulating guide disposed in a single heating device in a draw-texturing region. Recently, the yarn texturing speed becomes high, while the thickness of the yarn to be textured becomes small. As a result, when the twist stopping device is disposed near the entrance of the heating device, the viscosity resistance of the lubricant in the bearing of the twist stopping device or rolling friction of the rolling bearing is rapidly raised as the texturing speed is raised. Thus, there occur such problems as described below. For an example, referring to Fig. 11, when a polyester yarn, the thickness of which is 15 denier, is drawn and false twisted, the tension in the yarn located upstream of the twist stopping device (which is illustrated at the left portion in Fig. 11) becomes excessively small, since the rolling resistance of the twist stopping device is large compared with tension in the texturing yarn (e.g., the rolling resistance is about 4 to 5 g for a roller having a diameter of 30mm). Thus, the yarn passage is fluctuated at a position upstream of the twist stopping device or the yarn entangles around a feed roller disposed upstream of the twist stopping device, and operational conditions become unstable. If the tension in the texturing yarn is raised in order to prevent the yarn from the above-described entangling, the tension in the yarn located at the entrance of the heating device becomes around or higher than a drawing tension which is determined based on the yarn temperature located around the entrance of the heating device. Thus, the drawing point in the yarn passage where the drawing of the yarn occurs may be fluctuated along the yarn passage around the entrance of the heating device. Further, according to the fluctuation of the drawing point, the quality of the obtained textured yarn may be deteriorated, and unevenness in the dyeability may occur. Further, in the prior art disclosed in the above-described Japanese Utility Model Application Laid-open No. Sho 59-73378, since a twist stopping guide is disposed upstream of the heating device, twists imparted by the false twisting device run back along the yarn through the heating device to the twist stopping guide disposed upstream of the heating device, and they reach the drawing point or a portion near the drawing point. As a result, the drawing point is unstable due to the false twisting torque or the vibration of the yarn, and unevenness in the dyeability is observed in the obtained textured yarn. In addition, according to a conventional technology, in order to overcome a surging phenomenon, i.e., a drastic vibration of the yarn, caused by the false twisting device disposed downstream of the heating device and occurring in the yarn located upstream of the false twisting device, the tension in the yarn is enhanced over a tension which is generally required for false twisting operation. As a result, the tension in the yarn located at the entrance of the heating device is equal to or exceeds a tension around the maximum drawing tension which is determined based on the temperature of the yarn located at the entrance of the heating device. Thus, the drawing point in the yarn passage where the drawing of the yarn occurs may be fluctuated in a lengthwise region along the yarn passage around the entrance of the heating device. Further, according to the fluctuation of the drawing point, the quality of the obtained textured yarn may be deteriorated, and unevenness in the dyeability may occur. The above-described phenomena are remarkable especially in a yarn having a small thickness or in a yarn textured at a high speed where the tension is raised in order to prevent the surging phenomenon. Furthermore, according to the conventional technology disclosed in Japanese Utility Model Application Laid-open No. Sho 59-73378, the deflecting angles, i.e., the contacting angles, between a plurality of regulating guides and a yarn are substantially the same. Thus, the tension inclination between the entrance and the exit of the heating device is small, and accordingly, the drawing point is unstable. The drawing point becomes unstable especially due to the variation in false twisting torque caused by the false twisting device, the yarn vibration or variation in the yarn tension. Thus, the drawing point may move along the yarn passage in the yarn moving direction, that means the drawing point moves along the yarn portions having different twists therein, and unevenness in drawing operation, and accordingly, unevenness in the dyeability may occur. US-A-3,803,674 discloses an apparatus for heating thermoplastic yarn and several textile yarn processing machines in which this heater may be used. These machines include a false twisting machine, a machine in which yarn is first false twisted and then post-treated for the purpose of producing a set yarn, and a machine to simultaneously twist and post-treat false twist yarn. The post-treatment stage comprises a pair of feed rolls which provide an overfeed of the yarn such that the yarn arriving on the surface of a heater arranged downstream the feed rolls is partially relaxed. US-A-3,782,091 discloses a method and an apparatus for texturing yarns by false twisting, in which untextured yarn is drawn from a producer's package, threaded through an apparatus, and wound on yarn take-up means. The apparatus comprises a tension leveling device, an electric heater and a false twist device. A twist stop device is arranged close to the yarn exit from the heater, and a check device is arranged close to the downstream side of the false twist device. It is an object of the present invention to provide a draw-texturing apparatus by which a yarn, having a small thickness or comprising filaments with small filament denier, can be textured at a high speed, and the obtained textured yarn is free from unevenness in dyeability and have a high quality. It is another object of the present invention to provide a draw-texturing apparatus in which the drawing point in a yarn is stable against false twisting torque or a yarn vibration and by which the textured yarn being free from unevenness in dyeability and having a high quality can be obtained through a texturing operation of the yarn after a drawing operation. The invention is defined by appended claim 1. According to the present invention, since the twist stopping means is disposed in the heating means, the yarn can be subjected to the drawing operation at a portion upstream of the twist stopping means, i.e., at a portion where the yarn is free from the twists, and the drawing operation while the yarn is twisted is prevented. Accordingly, if the yarn is subjected to fluctuation due to unevenness in false twisting torque in the yarn or yarn vibration, the position of the drawing point can be stable. Accordingly, the yarn quality of the obtained textured yarn can be improved. According to another aspect of the present invention, the above-described objects are achieved by a yarn draw-texturing apparatus for drawing and false twisting a yarn comprising a false twisting device disposed at a downstream position, a heating device for completely or partially encircling in a non-touch manner the synthetic yarn along which twists imparted by the false twisting device run back so as to draw and false twist the yarn, and a twist stopping means disposed around an entrance of the heating device characterized in that a bearing of the twist stopping means is a fluid dynamic pressure bearing so that the tension in the yarn located at the entrance of the heating device is set at about a drawing tension of the yarn or lower than the drawing tension. Further, according to the present invention, provided is a yarn draw-texturing apparatus for drawing and false twisting a yarn comprising a false twisting device disposed at a downstream position, a heating device for completely or partially encircling in a non-touch manner the synthetic yarn along which twists imparted by the false twisting device run back characterized in that apparatus further comprises a resistance imparting means which is disposed in the heating device in such a manner that the tension in the yarn located near an entrance of the heating device is less than a drawing tension which is determined based on to a temperature of the yarn located near the entrance of the heating device. In addition, the present invention provide a yarn draw-texturing apparatus comprising a heating means for heating a running yarn and a false twisting means disposed downstream of the heating means for imparting twists to the yarn, characterized in that the heating means has a regulating means for stabilizing a drawing position of the yarn and a high resistance imparting means both disposed therein, and yarn resistance imparted by the high resistance imparting means is higher than a yarn resistance which the yarn receives at a position in the heating means and downstream of the high resistance imparting means. Finally, the present invention provides a method for draw-texturing a synthetic yarn in a draw-texturing apparatus comprising a heating device and a false twisting device disposed at a position downstream of the heating device wherein the yarn along which twists imparted by the false twisting device is passed through the heating device which entirely or partially encircles the yarn in a non-contacting manner, characterized in that a yarn resisting member is disposed at a position in the heating device and downstream of an entrance of the heating device away from the entrance by a predetermined distance in such a manner that the tension in the yarn located upstream of the resisting member is less than a drawing tension which is determined based on to a temperature of the yarn passing through the entrance of the heating device and the yarn resisting member, and that the tension in the yarn located downstream of the resisting member is higher than a drawing tension which is determined based on to a temperature of the yarn located near the yarn resisting member. According to the present invention, the resistance imparting means, the high resistance imparting means, or the resistance imparting member serves to reduce the run back of the twists imparted by the false twisting device and at the same time it creates difference in yarn tension between the yarns located upstream of and downstream thereof. The present invention will now be explained in detail referring to the attached drawings wherein some embodiments of the present invention are illustrated. In the drawings: Fig. 1 is a schematic side view of a draw-texturing apparatus according to the present invention; Fig. 2 is a cross sectional view of a heating means; Fig. 3 is a view seen in arrow A in Fig. 2; Fig. 4 is a cross sectional view of a twist stopping roller; Fig. 5 illustrate an embodiment of a heating device of the present invention, wherein: (a) is a cross sectional view; (b) and (c) are views seen in arrow B in Fig. 5(a); and (d) is a part of a cross sectional view similar to Fig. 5(a); Fig. 6 is a cross sectional view of a heating means of another embodiment; Fig. 7 is a schematic side vies of another draw-texturing apparatus of the present invention; Fig. 8 is a cross sectional view of the heating means illustrated in Fig. 7; Fig. 9 is a diagram of the present invention illustrating a tension in the yarn running a region from a position upstream of the twist stopping guide to the exit of the heating device and a tension at which drawing operation is possible and which is determined based on to the temperature of the yarn located near the entrance of the heating device; Fig. 10 illustrates another embodiment of a twist stopping roller; Fig. 11 is a diagram of a conventional technology illustrating a tension in the yarn running a region from a position upstream of the twist stopping guide to the exit of the heating device and a tension at which drawing operation is possible and which is determined based on to the temperature of the yarn located near the entrance of the heating device; Fig. 12 is a detailed view of another embodiment of a heating device of the present invention; Fig. 13 is a diagram illustrating a temperature of a yarn passing through a heating device; Fig. 14 is a diagram illustrating a tension in yarn passing through a heating device; Fig. 15 is a cross sectional view along line A-A in Fig. 8; Fig. 16 illustrates another embodiment, wherein: (a) is an elevation; and (b) is a cross sectional view along line B-B in Fig. 16 (a); Fig. 17 is an elevation of another embodiment; Fig. 18 is an elevation of a still other embodiment; and Fig. 19 is a cross sectional view of a further embodiment. Referring to Fig. 1, a yarn Y, which is a partially oriented yarn (POY) or an undrawn yarn (UD yarn) of a synthetic yarn, such as polyester or polyamide, is withdrawn from yarn supply 1 by means of a pair of withdrawing rollers 2a and 2b, and the yarn Y is drawn between a feed roller device 30 comprising a pair of nip rollers and a delivery roller device 6 similarly comprising a pair of nip roller. Between the feed roller device 30 and a delivery roller device 6, there are a heating device formed in an L-shape, a pair of stabilizing racks 4a and 4b disposed downstream of the heating device 3 and arranged in a reverse L-shape, and a false twisting device 5 for imparting twists to the yarn Y. The stabilizing racks 4a and 4b cool the yarn Y which has been heated by the heating device 3. The false twisting device 5 may be of a conventionally known type, such as a spindle type, a type comprising a plurality of spindles with a plural of discs and so on. The twists imparted to the yarn Y by the false twisting device 5 run back upstream along the yarn Y and are heat set at the heating device 3. If necessary, a second heater 31 is disposed at a position downstream of the delivery roller device 6, and the second heater may be omitted in some cases. The yarn Y is wound in a package 8 in a take up comprising a friction roller 7 and a cradle after it passes through the feed roller devices 9 and 10. The construction of the heating device 3 will now be explained with reference to Fig. 2. The heating device 3 of the illustrated embodiment is formed in an L-shape as illustrated in Figs. 1 and 2. The heating device 3 comprises a case 12 surrounding the L-shaped portion, sheath heaters 15 and 18 disposed in the case 12, heater plates 17 and 20 of the heating device 3 which are heated by the sheath heaters 15 and 18, respectively. The heater plates 17 and 20 have yarn regulating guides 16 and 19, which have grooves 16a and 19a formed at the center thereof, respectively (see Fig. 3), disposed thereon, respectively. the sheath heaters 15 and 18 may be replaced by another conventionally known heating member. A twist stopping roller 11 is rotatably supported at an intermediate portion of the heating device 3 formed in an L-shape. The twist stopping roller 11 is disposed on a support 26 so that the twist stopping roller 26 may be moved between a normal operational position illustrated by a solid line in Fig. 2 and a threading position illustrated by a phantom line. Thus, the heating device 3 is divided into two portions 13 and 14, one portion 13 locating upstream of the twist stopping roller 11 and the other portion 14 locating downstream of the twist stopping roller 11. Reference numeral 21 in Fig. 2 denotes a heat insulating material of the heating device 3. The detailed construction of the twist stopping roller 11 is illustrated in Fig. 4. The support 26 has a shaft 23 secured thereto by means of a nut 27. The shaft 23 has a plurality of V-shaped grooves 23a formed at the periphery thereof. The twist stopping body 22 is inserted onto a portion of the shaft 23 having the grooves 23a. Thus, the twist stopping roller 11 has a fluid dynamic pressure bearing formed between the shaft 23 and the twist stopping roller body 22. Flanges 24 and 25 have grooves for receiving thrust formed at the side of the twists stopping roller 11, and they are inserted onto the shaft 23, respectively. Thus, a pneumatic thrust bearing is formed by the grooves for receiving thrust, and the axial movement of the twist stopping roller 11 is prevented. The twist stopping roller body 22 has a plurality of blades 22a, which are common in a usual twist stopping roller, formed in a zigzag fashion at the surface thereof. In the present embodiment which has a construction as described above, the yarn Y withdrawn from the yarn supply 1 is drawn between the feed roller device 30 and the delivery roller device 6. In this case, the yarn Y is heated by the heating device 3 and is drawn at a draw ratio determined by the difference in speeds of the feed roller device 30 and the delivery roller device 6. Since the twist stopping roller 11 is disposed in the heating device 3, the twists imparted by the false twisting device 5 run back to the twist stopping roller 11. In this apparatus, the yarn Y has been drawn under a condition wherein run back of the twists is substantially prevented before it reaches the twist stopping roller 11. Since the drawn yarn Y is then subjected to the twists, the drawing point is stable regardless of the twists imparted by the false twisting device 5. Accordingly, the yarn quality of the obtained textured yarn becomes good. In the present embodiment, the yarn Y running in the heating device 3 is heated from the entrance of the heating device 3, and the twist stopping roller 11 is disposed at a position between the false twisting device 5 and a position where the yarn temperature thus heated exceed the glass transient temperature of the yarn Y. Thus, the yarn Y heated by the heating device 3 is heated from the entrance of the heating device 3 to a temperature higher than the glass transient temperature and the yarn Y is surely drawn between the entrance and the twist stopping roller 11. Another embodiment of the present invention will now be explained with reference to Fig. 5. In this embodiment, the heating device 3 is arranged in a substantially straight line as illustrated in Fig. 5 (a) but not in an L-shape. The twist stopping means is constructed with three rollers 31, 32 and 33 which are disposed in a zigzag fashion as illustrated in Fig. 5(b) which is seen in arrow B in Fig. 5(a). Similarly, in Fig. 5(c), a roller 32 and a pin 34 are disposed at positions away from a normal yarn passage. Thus, the yarn Y is deflected between the twist stopping means 32 and a roller 31 or a pin 34 which serves as a guide and which disposed upstream of the twist stopping means, i.e., the roller 32. Accordingly, twists imparted by the false twisting device 5 do not run back upstream beyond the twist stopping means 11. The yarn Y is drawn before it reaches the twist stopping means, and then the drawn yarn is twisted. Especially when the yarn Y is deflected between the roller 32 which is a twist stopping means and the guide pin 34 as illustrated in Fig. 5 (c) so that difference in tension in the yarn located upstream of the yarn guide and the yarn located downstream of the guide is caused due to the friction between the yarn Y and the guide, the yarn Y can be surely drawn at the guide. In an alternative embodiment, a roller 35 having a rotating axis perpendicular to a plane on which Fig. 5(a) is illustrated is disposed between the yarn regulating guides 19 of the heating plates as illustrated in Fig. 5 (d), and the yarn Y passes by the yarn regulating guides 19 is pressed by the roller 35. The roller 35 serves as a twist stopping means and stops twists run back along the yarn Y. Since the position where the roller 35 is disposed is downstream of a position where the yarn temperature reaches the glass transient temperature, the drawing point of the yarn Y is secured between the entrance of the heating device and the roller 35, and the yarn Y is imparted with twists after securing of the drawing point, and the drawing point does not vary. Especially when a high resistance imparting means is disposed in the heating device as illustrated in Fig. 5(c), it is preferred that the high resistance imparting means is so arranged that the yarn resistance imparted by the high resistance imparting means is higher than a yarn resistance which the yarn is subjected to between the high resistance imparting means and the twist stopping means. Thus, the drawing point is surely secured by means of the high resistance imparting means. Although the guide 16 is disposed upstream of the twist stopping means 11 and the yarn Y is deflected between the guide 16 and the twist stopping means 11 so that difference in tension is caused in the yarn located upstream of the guide 16 and in the yarn located downstream of the guide 16 by means of friction between the yarn and the guide 16 in the above-described embodiment illustrated in Fig. 2, according to the present invention, guide may be disposed downstream of the twist stopping means and the yarn Y may be deflected between the guide and the twist stopping means so that difference in tension is caused in the yarn located upstream of the guide and in the yarn located downstream of the guide by means of friction between the yarn and the guide. An example of such an embodiment is illustrated in Fig. 6. In Fig. 6, a twist stopping roller 11 is disposed in the heating device 3, and twists imparted by the false twisting device 5 run back to the twist stopping roller 11. In this embodiment, the yarn Y is heated to a temperature around the glass transient temperature before it reaches the twist stopping roller 11, and the yarn Y is subjected to a resistance by a guide pin 34 under such a condition. The yarn Y is drawn at a position downstream of the guide pin 34 under a tension higher than a drawing tension which is determined based on the yarn temperature. Thus, the yarn Y is surely and stably drawn. The tension in the yarn Y located upstream of the guide pin 34 is so set that it is lower than a drawing tension determined based on the temperature of the yarn located upstream of the guide pin 34. The construction of the twist stopping roller is similar to that explained above with reference to Fig. 4, and the yarn regulating guides 19 have grooves 19a similar to the guide 19 illustrated in Fig. 3. Fig. 7 is a schematic side view of a draw-texturing apparatus of another embodiment according to the present invention, and Fig. 8 illustrates the details of the heating device 3. In the above-described draw-texturing apparatus illustrated in Fig. 1, the twist stopping roller 11 was disposed at the corner of the L-shape. Contrary to this, in the draw-texturing apparatus illustrated in Fig. 7, the heating device 3 is formed in a substantially straight form and the twist stopping roller 11 is disposed upstream of the heating device 3. The twist stopping roller 11 has a construction similar to that illustrated in Fig. 4. The yarn Y is wrapped around the blades 22a of the twist stopping roller 11 and is deflected so that run back of twists along the yarn Y is stopped. The construction of the heating device 3 of the present embodiment will now be explained with reference to Fig. 8. The heating device 3 of this embodiment comprises a case 13, sheath heaters 15 and 18 disposed in the case 13 and heater plates 17 and 20 heated by the sheath heaters 15 and 18, respectively. The heater plates 17 and 20 have yarn regulating guides 19, having grooves 19a for guiding yarn at the center thereof, disposed at the surface thereof. The sheath heaters may be replaced by another known heating element. A guide 40 serving as a resisting means presses the yarn from the above. In a specific example, the temperature of the heating device was set at 550 o C for 0.3 m from the entrance thereof and at 290 o C for a region between 0.3 m and 1 m. Under these conditions, a polyester POY was drawn and textured to obtain for example a textured yarn of 15 denier/8 filaments. Although the heating device 3 was divided into two portion in this embodiment, the heating device 3 may be formed in a single heater or may be composed of a plurality of portions, the number of which is larger than two. It is preferred that the guide 40 serving as the resisting means has a portion, the radius of curvature of which is larger than 2 mm, for contacting with the yarn at the center thereof so that scattering of the yarn is reduced. The guide 40 has a heating means and a sensor disposed therein so that the guide is controlled to a predetermined temperature according to the present embodiment. Thus, the drawing point in the yarn Y is surely secured by heating the guide 40 to a predetermined temperature and by reducing the tension in the yarn Y located upstream of the guide 40 by means of the resistance imparted by the guide 40. Fig. 9 is a diagram of the present invention illustrating a tension in the yarn running a region from a position upstream of the twist stopping guide to the exit of the heating device and a tension at which drawing operation is possible, i.e., the drawing tension L, and which is determined based on to the temperature of the yarn located near the entrance of the heating device. As illustrated in Fig. 9, since the rotating resistance of the twist stopping means is not large compared with the texturing tension in the yarn, the tension in the yarn located upstream of the twist stopping means does not become excessively small [please compare the left portions of the twist stopping means in Fig. 9 (the embodiment of the present invention) and Fig. 11 (comparison)]. Accordingly, the yarn is not fluctuated at position upstream of the twist stopping means, and therefore, the yarn does not entangle around rollers disposed upstream of the twist stopping means, and the operational condition becomes stable. Although the resisting member 40 was disposed in the heating device in the present embodiment, unexpected advantages similar to those of the above-described embodiment can be achieved in an embodiment without such a resisting member 40. Although a fluid dynamic bearing is applied to the twist stopping roller 11 in the present embodiment, such as a fluid static pressure bearing as illustrated in Fig. 10 wherein compressed air is supplied may be used. In Fig. 10, compressed air is supplied from a compressed air supply 29 through a compressed air supplying hole 24b formed in the shaft 24 and forms a bearing air layer between the shaft 24 and the twist stopping roller 23. Reference numeral 50 denotes an O-ring. The fluid bearing engaging portion may be formed in a spherical construction which can support both radial and thrust forces. Alternatively, the shaft may be formed in a cylinder for supporting radial load and a thrust washer may be engaged with the shaft to support thrust so that radial and thrust forces are independently supported. An embodiment of a still other embodiment of the heating device 3 will now be explained with reference to Fig. 12. The draw-texturing apparatus in which the heating device 3 is mounted is similar to that illustrated in Fig. 7. The heating device 3 of the illustrated embodiment is outwardly bent in an L-shape as illustrated in Fig. 12 and comprises a case 13, sheath heaters 15 and 18 disposed in the case 13 and heater plates 17 and 20 of the heating device 3 heated by the sheath heaters 15 and 18, respectively. The heater plates 17 and 20 have yarn regulating guides 19, having grooves 19a for guiding yarn at the center thereof, disposed at the surface thereof. The sheath heaters 15 and 18 may be replaced by another known heating element. The heating device 3 is formed in an L-shape. A guide 40 serving as a resisting means is disposed at the bent portion of the heating device. It is preferred that the guide 40 serving as the resisting means has a portion, the radius of curvature of which is larger than 2 mm, for contacting with the yarn at the center thereof so that scattering of the yarn is reduced. Although the heating device 3 was divided into two portion in the present embodiment, the heating device 3 may be formed in a single heater or may be composed of a plurality of portions, the number of which is larger than two. Further, the two heater plates 17 and 20 of the heating device 3 may be aligned in a substantially straight line as illustrated in Fig. 8. Furthermore, the yarn Y may pass through the inside of the heater plates 17 and 20 formed in an L-shape as illustrated in Fig. 19. Fig. 15 is a cross sectional view taken along line A-A in Fig.8 and clearly illustrates the attaching condition of the yarn regulating guide 40 to the cover 21 of the heating device 3. In another embodiment, yarn regulating guides 100, 101 and 102 having yarn guiding grooves 100a, 101a and 102a, respectively, may be fixedly disposed as illustrated in Fig. 16(a). Although the yarn regulating guides 100, 101 and 102 are fixedly disposed as illustrated in Fig. 16(b), the yarn regulating guide 103 may be laterally moved so that the yarn guiding grooves 100a, 101a and 102a align in a straight line upon threading operation, and the yarn regulating guide 103 may be returned to a position as illustrated in Fig. 16 (a) after threading operation. In the above-described embodiment illustrated in Fig. 12, the yarn regulating guides 19 of the heating device 3 are so arranged that the yarn Y guided by the yarn regulating guides forms a circular yarn passages with a large radius of curvature of R in a plane on which Fig. 12 is illustrated. The yarn passage may be straight or may be formed in a zigzag passage by means of the resisting member 40 and the yarn guides 41 as illustrated in Figs. 17 and 18. In any cases, the tension of the yarn Y located upstream the resisting member 40 should be less than the drawing tension which is determined based on the yarn temperature. Fig. 13 is a diagram illustrating the temperature of the yarn passing through the heating device 3. In this example, the temperature of the heating device 3 was set at 550 o C for 0.3 m from the entrance thereof and at 290 o C for a region between 0.3 m and 1 m. Fig. 13 illustrates the temperature cf the yarn Y when a polyester POY of 125 denier/36 filament was drawn at a draw ratio of 1.66 to obtain a textured yarn of 75 denier under the above-described conditions. Fig. 14 is a diagram illustrating a tension in yarn Y passing through a heating device 3 according to the embodiment illustrated in Fig. 12 and a diagram illustrating a tension in yarn according to a conventional apparatus. According to the embodiment of the present invention, the tension in the yarn (designated by solid line L 2 , T 0 at the entrance (F) of the heater and T 1 at the exit (E) of the heater) passing through two heater plates 17 and 20 gradually increases at every yarn regulating guides 19 due to the frictional resistance between the yarn regulating guides 19 disposed along the yarn passage and the yarn Y. Further, a guide 40 serving as a resisting member is disposed between the heater plates 17 and 20, and accordingly, a large difference in tension is caused between the upstream and the downstream of the guide 40 (see point G). Contrary to this, according to the conventional apparatus, two heater plates 17 and 20 are disposed in a substantially straight line, and the heater plates 17 and 20 have a plurality of yarn regulating guides 19 which is determined based on to Fig. 12 with the heater plates 17 and 20 arranged in a substantially straight line. The tension in the yarn (designated by broken line L 1 ) passing through two heater plates 17 and 20 gradually increases at every yarn regulating guides 19 due to the frictional resistance between the yarn regulating guides disposed along the yarn passage and the yarn. As a whole, a tension inclination D to E is formed from the entrance to the exit of the heating device. The amount of the tension at the exit (E) is so set that the running yarn does not cause surging phenomenon. Although the tension in the yarn of the present invention designated by solid line L 2 should overlap with the tension in the yarn according to the conventional apparatus designated by broken line L 1 at the right halves of the diagrams, in order to clarify the illustration, the tension in the yarn according to the conventional apparatus designated by broken line L 1 is slightly moved upwardly relative to the tension in the yarn of the present invention designated by solid line L 2 in Fig. 14. The drawing tension, at which the yarn can be drawn and determined by the temperature of the yarn, is illustrated by L 3 . L 1 and L 3 are very close to each other or are overlapping with each other near the entrance of the heating device 3. According to the present invention, a large tension difference is formed relative to the drawing tension, which is determined based on the yarn temperature, at a position upstream of the guide 40. Accordingly, the drawing point of the yarn is stable regardless of disturbance, such as variation in temperature, variation in false twisting torque. More specifically, the tension L 1 tends to move in a direction designated by arrows A and B due to the disturbance during the texturing operation, such as variation in the number of twists, a raising current of air, withdrawal tension of the yarn supply, unevenness in thickness or vibration of the yarn, while the drawing tension tends to move in a direction designated by arrow C. Thus, the point in the yarn where the drawing point occurs varies. When the drawing point varies excessively, the drawing point moves near the entrance of the heating device, thus, yarn quality is deteriorated and unevenness in dyeability occurs. However, according to the present invention, a resisting member 40 for imparting resistance to the yarn is disposed at a position where the temperature of the yarn is stable, and the tension in the yarn located upstream of the resisting member 40 is set lower than the drawing tension which is determined based on the yarn temperature. Accordingly, even if such disturbances as described above occur, the drawing point is secured by the position of the resisting member, and a textured yarn having a high quality and being free from unevenness in dyeability can be obtained. It is preferred that the tension at the entrance of the heating device is set not more than 0.9 times as much as the drawing tension which is determined based on the temperature of the yarn located at a region between the entrance of the heating device and the resisting member. According to the present embodiment, the heating device 3 is formed along the construction illustrated in Fig. 12, and the heating device X and the heating device Y are arranged in an L-shape. The contacting angle between the yarn and the guide 40 is set  and difference in tension is formed between the yarn located upstream of the guide 40 and the yarn located downstream of the guide 40. In this embodiment, the friction coefficient between the guide and the yarn was 0.4 and the contacting angle  was 25 o . Especially when the thickness of the yarn is very small, the rotating resistance of the twist stopping guide remarkably affects on the yarn quality of the obtained textured yarn. Accordingly, it is preferred that a pneumatic bearing, which may be of a dynamic pressure type, of a static pressure type or combination of them, is used for the the bearing for supporting the twist stopping guide, or that the twist stopping guide is driven at a predetermined speed. In the present embodiment, the contacting angle between the resisting member and the yarn is set at a constant amount. However, the contacting angle may be altered, and the tension in yarn may be fed back after the tension in the yarn at the entrance of the heating device is detected. In a further embodiment of a draw-texturing apparatus for drawing and texturing a yarn comprising a heating apparatus through which the yarn passes and a false twisting device disposed at position downstream of the heating device and imparting twists to the yarn, the heating device may have a yarn regulating means for securing the drawing point of the yarn and a means for imparting high resistance to the yarn both disposed therein and the resistance applied to the yarn by the high resistance imparting means may be set larger than the resistance which the yarn receives at a position in the heating device and downstream of the high resistance imparting means. It is preferred that the position where the yarn is most deflected by the regulating means is located downstream of a point where the yarn temperature is higher than the glass transient temperature of the yarn.

Claims: A yarn draw-texturing apparatus for drawing and false twisting a yarn (Y) comprising a feed roller means (30), a heating means (3) for heating the running yarn (Y), a false twisting means (5), disposed downstream of said heating means (3), for imparting twists to said yarn (Y) and a delivery roller means (6), disposed downstream of said false twisting means (5), for drawing said yarn (Y) between said feed roller means (30) and said delivery roller means (6) characterized in that said apparatus further comprises a twist stopping means (11, 32, 35) for stopping run back of said twists imparted by said false twisting means (5) or a yarn resisting means (40) for reducing said run back of said twists which means (11, 32, 35, 40) is disposed in said heating means (3) at a position between said false twisting means (5) and a position where a temperature of said yarn (Y) passing through said heating means (3) is higher than a glass transient temperature of said yarn (Y). A yarn draw-texturing apparatus according to claim 1, characterized in that said twist stopping means (11) is a rotatable roller (22) and a bearing (23a) of said roller (22) is a fluid dynamic or static pressure bearing. A yarn draw-texturing apparatus according to claim 1, characterized in that said apparatus further comprises a guide (16) which is disposed upstream of said twist stopping means (11) and said yarn is deflected between said guide (16) and said twist stopping means (11) so that difference in tension is caused in the yarn (Y) located upstream of said guide (16) and in the yarn (Y) located downstream of said guide (16) by means of friction between said yarn (Y) and said guide (16). A yarn draw-texturing apparatus according to claim 1, characterized in that said apparatus further comprises a high resistance imparting means (40) which is disposed upstream of said twist stopping means (11, 32, 35) and in said heating means (3), and yarn resistance imparted by said high resistance imparting means (40) is higher than yarn resistance which said yarn (Y) is subjected to between said high resistance imparting means (40) and said twist stopping means (11, 32, 35). A yarn draw-texturing apparatus according to claim 1, characterized in that said apparatus further comprises a guide (34) which is disposed downstream of said twist stopping means (11) and said yarn (Y) is deflected between said twist stopping means (11) and said guide (34) so that difference in tension is caused in the yarn (Y) located upstream of said guide (34) and in the yarn (Y) located downstream of said guide (34) by means of friction between said yarn (Y) and said guide (34). A yarn draw-texturing apparatus according to claim 1, 3 or 5, characterized in that said resistance imparting means (40) is provided with a means for heating said resistance imparting means. A yarn draw-texturing apparatus according to claim 1, characterized in that said yarn resisting means (40) for reducing said run back of said twists is disposed in said heating means (3) in such a manner that the tension in the yarn (Y) located near an entrance of said heating means (3) is less than a drawing tension which is determined based on to a temperature of said yarn (Y) located near said entrance of said heating means (3). A yarn draw-texturing apparatus according to claim 1, characterized in that said heating means (3) has a regulating means for stabilizing a drawing position of said yarn (Y) and said high resistance imparting means both disposed therein, and yarn resistance imparted by said high resistance imparting means is higher than yarn resistance which said yarn (Y) receives at a position in said heating means (3) and downstream of said high resistance imparting means. A yarn draw-texturing apparatus according to claim 6, characterized in that said regulating means is so disposed that a position where said yarn is deflected by said regulating means is located downstream of a position where a temperature of said yarn (Y) exceeds a glass transient temperature of said yarn (Y). A method for draw-texturing a synthetic yarn (Y) in a draw-texturing apparatus comprising a feed roller means (30),a heating device (3), a false twisting device (5) disposed at a position downstream of said heating device wherein said yarn (Y) along which twists imparted by said false twisting device (5) is passed through said heating device (3) which entirely or partially encircles said yarn (Y) in a non-contacting manner, and a delivery roller means (6), disposed downstream of said false twisting means (5), for drawing said yarn (Y) between said feed roller means (3) and said delivery roller means (6) characterized in that a yarn resisting member is disposed at a position in said heating device (3) and downstream of an entrance of said heating device (3) away from said entrance by a predetermined distance in such a manner that the tension in the yarn (Y) located upstream of said resisting member is less than a drawing tension which is determined based on to a temperature of said yarn (Y) passing through said entrance of said heating device (3) and said yarn resisting member, and that the tension in the yarn (Y) located downstream of said resisting member is higher than a drawing tension which is determined based on to a temperature of said yarn (Y) located near said yarn resisting member.

Inventors: SUGIOKA TAKAMI, SUGIOKA, TAKAMI, SUGIOKA, TAKAMI, C/O TEIJIN SEIKI CO., LTD.
Applicants: TEIJIN SEIKI CO LTD, TEIJIN SEIKI CO. LTD.
Application year: 1994
Main classification: D02G1
IPC codes: D02J13, D02G1